Sewing on a sewing machine normally requires that the operator hold a piece of cloth being sewn in front of a sewing needle to slightly push the cloth in a direction of feed by hand on a bed of the sewing machine so that the piece of cloth will be guided to form a desired line of stitches thereon. The above cloth guiding operation is however difficult to carry out on a portable sewing machine since the latter has a relatively small bed which has only quite a small area available for the operator to guide the cloth thereon in front of the sewing needle. The difficulty can be overcome by either providing an enlarged bed extending toward the operator or attaching an auxiliary bed. These proposals are disadvantageous, however, in that the bed then projects toward the operator and interferes with sewing operation. Furthermore, the enlarged bed needs a relatively large or bulky casing for housing the sewing machine. The auxiliary bed is required to be attached and detached each time the sewing machine is used and stored.
The working surface on the bed could be increased, without accompanying an increase in the size of a sewing machine, by displacing stitch forming mechanisms such as a hook and a sewing needle rearward or downstream in a direction of feed of a piece of cloth to be sewn. While a space could be available for the rearward displacement of the hook in the bed on a sewing machine with a horizontally rotatable hook which is disposed in front of a sewing needle, the arm and head of the sewing machine lack sufficient space for displacing a needle bar drive mechanism rearward. Displacing the needle bar drive mechanism rearward requires the stitch forming mechanisms to undergo a large design change. A sewing machine in which a hook is located behind a sewing needle has no space available for the hook to be brought into a retracted position.
In addition to the rearward displacement of the hook, a stand on the sewing machine bed could be tilted backward to displace the arm and head rearward to increase the working surface on the bed. However, the center of gravity of the sewing machine would then be shifted backward, rendering the sewing machine less positionally stable and susceptible to vibrations due to the inertia of the moving parts.